The three-time All-Star outfielder was activated from the disabled list Monday in time for the second-place Indians‘ most important series of the season _ a three-game home set against the first-place Detroit Tigers.

“I’m excited,” Sizemore said. “This is where you want to be. You want to be contending in September.”

Manager Manny Acta was happy to put Sizemore in the leadoff spot in the batting order, playing center field, as Cleveland sought to trim the Tigers‘ 6 1/2-game lead. Acta said he hopes second baseman Jason Kipnis, out since Aug. 14 with a strained hamstring, could be activated this week, but third baseman Jack Hannahan will be out “a minimum of five to seven days.” Hannahan left Sunday’s game in Kansas City with a strained left calf.

“Just having Grady in the clubhouse is great,” Acta said. “He said he was ready, so we might as well have him up here.”

Sizemore had abdominal surgery July 21. He opened the season on the DL as he recovered from surgery on his left knee in May 2010. He then hurt his right knee and sustained a hernia on the same play while sliding into a base this May.

“I’m not 100 percent, but I don’t know if you are ever 100 percent,” Sizemore said. “There’s going to be a little rust, but I want to go out and help.”

Acta said that if the Indians were not trying to track down the Tigers, he would prefer that Sizemore had remained on an injury rehab assignment in the minors.

“If we were not in this situation, we could give him more time,” Acta said. “He is not going to play every day. The days he gets off, he is going to be completely off. No pinch hitting, no pinch running, no defensive replacement. Off.

“It takes a lot for him to get ready and we’re not going to push that.”

The Indians have been inundated with injuries all season. Sizemore, outfielder Shin-Soo Choo and designated hitter Travis Hafner, the team’s top three offensive players, have all missed large chunks of time with various injuries. Outfielder Michael Brantley is out for the season after having wrist surgery. Hafner and Choo, along with starting pitchers Josh Tomlin and Carlos Carrasco, remain on the DL, though the Indians are optimistic all except perhaps Carrasco can return sometime this month.

Acta said that he would not have believed it if anyone had told him in spring training that the Indians would lose so many players to injury and still be in contention in September.

“Credit the pitching staff,” Acta said. “We would not be where we are without them. I’m glad we’re still fighting for this. I said in March that we could not afford to lose players like Grady, Hafner and Choo. We lost them all. Amazingly enough, we have been able to survive.”